Baths or reservoirs for holding a plating bath that includes at least one material, such as a metal, to be is plated on a substrate are used in a wide variety of applications. For example, plating baths are commonly used in microelectronic device manufacturing. According to one example, baths are utilized for electroplating and for electroless plating on substrates.
Composition of plating baths and conditions within the plating bath must be carefully controlled to produce deposition of a desired quality of desired metal(s) on a substrate. Plating rate, uniformity, and deposit quality may be affected by a variety of factors. For example, one parameter that may affect rate, uniformity, and deposit quality of plating is concentration of chemicals in the plating bath as well as uniform distribution of the chemicals during production.
Along these lines, it is desirable to maintain the plating bath solution as close as possible to ideal conditions for plating. However, as the plating process proceeds, the characteristics of the solution, such as concentration and uniformity of chemicals, change as chemicals are used up in the plating process and components of the plating bath, such as surfactants, break down chemically and various byproducts build up.
According to standard practice, materials making up the plating bath typically are added individually directly to the bath. Once material is added to the bath, a period of time must pass before the material will be uniformly distributed throughout the plating bath. As can be appreciated, differential concentration of a material in the plating bath can with time result in non-uniform amounts plating, distribution and variable deposit quality. For example, the quality of films plated relatively later may be inferior to the quality of earlier plated films.